Many of the most challenging contaminated sediment sites awaiting effective remediation exhibit separate phase contamination (nonaqueous phase liquids or NAPLs), or mobile aromatic or chlorinated solvents. Conventional sediment remedial approaches, including dredging and capping, are not designed nor effective for the management of fluid phase contaminants. The use of a low permeability cap provides opportunities to control contaminant migration and simultaneously introduce treatment in the underlying sediment without loss of reagent or contaminant. Further, by maintaining hydraulic control, the contaminants or the treated residual can be funneled to a relatively small area, or "gate", for further treatment of any residual contamination. The proposed research is designed to develop this novel remedial approach that is an adaptation of proven funnel and gate technologies for groundwater control. Specific treatment technologies to be evaluated and developed include the use of organoclays for the sorption and stabilization of NAPLs, zero-valent iron for the reductive dechlorination of chlorinated solvents and enhanced biological treatment for the control of both aromatic and chlorinated solvents. The project will test the broad hypotheses that A funneling cap can effectively contain contaminants as well as introduced reagents beneath the cap and effectively channel interstitial fluids (water or NAPL) to a collection or treatment gate Slurries of treatment media, specifically organo-modified clays for NAPL stabilization, zero valent iron for encouragement of reductive dechlorination, or reagents encouraging biological degradation, can be introduced beneath a low permeability cap and stabilize or encourage reductive treatment of non aqueous and aqueous contaminants Treatment gates composed of reactive materials or encouraging biological degradation, either alone or in combination, can effectively manage residual contamination from the in-situ treatment zone The primary goal of the proposed research is control of exposure and risk to human health and the environment at the sediment-water interface. The resulting reduction in exposure and risk to benthic and aquatic organisms will eliminate human food chain exposure to contaminants in sediments.